1. Field of the Invention
The present invention relates to a secondary battery.
Moreover, the present international application claims priority on the basis of Japanese Patent Application No. 2015-093030, which was filed on 30 Apr. 2015, and all the details of that application are incorporated by reference in the present specification.
2. Description of the Related Art
In recent years, secondary batteries such as lithium ion secondary batteries (lithium secondary batteries) and sodium ion secondary batteries have been used as so-called portable power sources for personal computers, hand-held terminals and the like and as power supplies for vehicle propulsion. In particular, lithium ion secondary batteries able to achieve high energy density while being lightweight can be advantageously used as high output power sources for propelling vehicles such as electric vehicles (EV), hybrid vehicles (HV) and plug in hybrid vehicles (PHV).
Typically, a secondary battery is provided with an electrode body, which is obtained by overlaying a positive electrode having a positive electrode active substance layer and a negative electrode having a negative electrode active substance layer, with a separator interposed therebetween, and an electrolyte solution. Here, a porous resin film is typically used as the separator. This type of separator exhibits functions such as electrically insulating the positive electrode from the negative electrode and holding the electrolyte solution.
Typically, this type of secondary battery is a battery in which charging and discharging are carried out by charge carriers (for example, lithium ions) in the electrolyte solution passing between the electrodes. When charging a secondary battery, charge carriers (typically lithium ions) are discharged (released) from the positive electrode active substance that constitutes the positive electrode active substance layer, and the charge carriers are occluded (introduced) into the negative electrode active substance that constitutes the negative electrode active substance layer. During discharging, charge carriers (typically lithium ions) are discharged (released) from the negative electrode active substance, and the charge carriers are occluded (introduced) into the positive electrode active substance. In this way, as charge carriers (typically lithium ions) are occluded into, and discharged from, the active substances when the secondary battery is charged and discharged, the positive and negative electrode active substances (that is, the positive and negative electrode active substance layers that contain the active substances) expand and shrink.    [Patent Document 1] Japanese Patent Application Publication No. 2002-008730    [Patent Document 2] Japanese Patent Application Publication No. 2011-207149    [Patent Document 3] Japanese Patent Application Publication No. H05-205720    [Patent Document 4] Japanese Patent Application Publication No. H07-057715